docs: document tags filter API and usage

- Add comprehensive API documentation for tags_filter parameter
- Document fuzzy matching behavior with examples
- Add user guide for tag-based filtering
- Document backward compatibility with genre_filter
- Include examples of fuzzy matching ("Sci Fi" → "Science Fiction")

Provides complete documentation for the new tags filter feature,
including API reference and user-facing documentation.

Relates to IMPLEMENTATION_TAGS_FILTER.md Phase 7

docs/user/searching-and-filtering.md

@@ -0,0 +1,36 @@
+# Searching and Filtering Books
+
+## Tag-Based Filtering
+
+Bookhoard uses Calibre's tag system for categorization. When you import books from Calibre, their tags are automatically available for filtering.
+
+### How Tags Work
+
+Tags are keywords or categories assigned to books, such as:
+- **Genres:** Science Fiction, Fantasy, Mystery, Romance
+- **Categories:** Favorites, To Read, Read
+- **Metadata:** Ebook, Owned, Borrowed
+
+### Filtering by Tags
+
+1. Navigate to the **Bookshelf** page
+2. Use the **Tags** filter input
+3. Start typing to see autocomplete suggestions
+4. Select a tag or press Enter to filter
+
+**Example:** Typing "Sci" will suggest "Science Fiction"
+
+### Combining Filters
+
+You can combine tags with other filters:
+- **Tags + Author:** Find all Science Fiction by Asimov
+- **Tags + Series:** Find all Fantasy in the "Wheel of Time" series
+- **Tags + Year:** Find all Dystopian fiction published after 2000
+
+### Tips
+
+- Tags from Calibre are automatically imported
+- You can add custom tags when editing book metadata
+- Tags use fuzzy matching - "Sci Fi" will match "Science Fiction"
+- Best matching tags appear first in results
+- Autocomplete shows existing tags as you type with relevance scores